Water heater



1929. F. o. WADSWORTH 1,738,086

WATER HEATER Filed Jan- 5, 1923 3 Sheets-Sheet 2 4 m 4/ I 1 M Dec. 3,1929. F. o. WADSWORTH 1,738,086

WATER HEATER Filed Jan. 3, 1923 3 Sheets-Sheet 5 Inventor.

Patented Dec. 3, 1929 UNITED STATES PATENT OFFICE WATER HEATERApplication filed January 8, 1923. Serial No. 610,471.

My invention relates generically to apparatus for heating liquids, andparticularly to that type of structure that is generally designated aninstantaneous hot water heater. The generic object of the presentimprovements is to produce a simple, easily fabricated, reliable andeflicient species of apparatus, which will be less expensive toconstruct, and also more economical in operation, than the various formsof heaters now used for the same purpose.

A more specific object of this invention is to substantially increasethe efficiency of fuel consumption, and the percentage of ab- 13sorption of the heat so generated, without increasing the complexity orfirst cost of the heat generating and the heat absorbing elements.

Another particular purpose of my present invention is to provide a verysimple and fool proof mechanism, for automatically turning on, orcutting off, the supply of fuel to the heating burners, which isactuated by the kinetic or physical flow of fluid through 95 the heatingelements, and which is also controlled by the temperature of the flowingliquid, so that fuel is consumed only when that temperature is below apreadjusted and predetermined point. Or stated more explicitly thisparticular object of the invention is the provision of a velocitycontrolled device (as contra-distinguished from a pressure regulateddevice) which will act instantaneously in opening or closing a fuelsupply valve whenever liquid begins or ceases to flow through theapparatusindependently of any variations of hydrostatic or hydraulicpressure conditions thereinand which will also act with equal promptnessin intermittently closing and reopening the said valve during thecontinuation of the flow, whenever the temperature of the liquid risesabove or falls below a predetermlned point. I

A further object of these im rovements is to eliminate any substantialresistance to the movements of thevelocity-actuated-temperature-governed valve-mechanism, and therebyincrease the sensitiveness and reliability of the fuel controllingdevices; and as one means for accomplishin this object I provide acombination of exible metallic bellows or sylphon elements which arearranged to act directly on the fuel supply valve without theintervention or use of any pistons, guides, packing boxes or similarfrictionally retarded members ;thereby avoiding the difficulties thatresult from the corrosion, or seizing and sticking of difiicultlyaccessible or unlubricated parts of the working mechanism.

Still another purpose of the present improvements is the provision of avery simple, compact, and sensitive form of thermostat, which has alarge direct range of action for very small changes of temperature inthe flowing water-and is thus capable of effecting the necessarymovements of the thermostatic control devices without the use ofmultiplying levers or other similar instrumentalitiesand which servesonly to direct the application of. the velocity produced forces withoutitself exerting a great amount of motive energy.

In order that these, and other features and advantages of this inventionmay be fully understood by those skilled in this art, I have shown, andhereinafter describe, several alternative forms of my improved waterheater construction; but these are to be regarded as illustrative only,and not as limiting the scope of application of these improvements.

In the accompanying drawings:

Fig. 1 is a. composite view of one exemplification of my invention,which shows a portion of this construction in front elevation, and theremaining portion thereof in vertical section on a central plane; Fig. 2is a sectional plan view on the plane 22 of Fig. 1; Fig. 3 is a verticalsection on a larger scale, through the control mechanism of thisoranization; Fig. 4 is another vertical section t irough one of theheating burners; Figs. 5 and 6 are fragmentary detail views showingcertain alternative heating coil constructions;

Fig. 7 is a side elevation of a second form of and 12 are verticalsections through two other forms of control devices that may be used inplace of those shown in Figs. 3 and 9; Fig. 13 is asimilar section ofstill another form of valve actuating mechanism that embodies certainfeatures of my present improvements and which may also be used inconjunction with the general constructions depicted in Figs. 1, 2, 7 and8; and Figs. 14 and 15 are diagrams illustrating one of the specificfeatures of advantage of my'preferred forms of heating coils as shown inFigs. 1 and 5 or 8 and 9. i

The organization shown on the first sheet of my drawingsFigs. 1 to 4inclusive-comprises a cylindrical shell 1, which is closed at the bottomby a plate, 3, and is provided with a concentric sheet metal jacket 4,that forms therewith a narrow annular air space 5. A short closed drum 6is fitted closely in the lower slightly contracted end of the shell 1,and is held at a short distance above the bottom plate 3 by the centralfoot or lug 7. The upper end of the annular space 5 is in communicationwith the external air through I a row of openings 10 in the jacket 4;and the lower portion of this space communicates with the chamberbetween the drum 6 and the plate 3 through the series of transverseports 11 in the wall of the shell 3. The drum 6 carries an inner andouter row of gas burners 1212 etc., the detail construction of which isillustrated in Fig. 4. As there shown each of these burners consists ofa hollow stem support 13, which is screwed into the lower head of thedrum 6 and projects up through a larger opening in the upper endthereof; a mixing tube 14 which is threaded over the upper enlarged headof the stem 13 and is screwed down thereon until its lower flanged endis in sealedcontact with the drum head; and a perforated hood or cap 15which is screwed onto the upper end of the mixing tube 14. The head ofthe stem 13 is perforated with one or more restricted ducts 16 for thepassage of gas from the interior of the drum 6 to the mixing tube 14;and the top of the latter is preferably covered with supply of gas tothe burners 12; and a smaller independent connection 20 leads from thepilot light 21-which is located at a convenient point in the combustionchamber containing theburners 12to the main fuel supply conduit 22.

The operation of that portion of the organization which has thus farbeen described is as follows: When gas is admitted to the conduit 18 (inthe manner to be explained later) it fills the interior of the drum 6and issues through the ducts 16 in a series of high velocity jets whichare thoroughly mixed with the streams of air that are coincidently drawnupward through the stems 13, from the chamber between the drum 6 and theplate 3. The mixed gas and air flows upwardly, through the tubes 14, andthe screens 17, and outwardly through the perforated or slotted sides ofthe caps 15, and is ignited by the constantly burning pilot light 21.The upward movement of the air from the lower chamber results in acorresponding inflow of airthrough the row of openings 10, downwardlythrough the annular space 5, and inwardly through the series of radialports 11- to the said chamber; and this inflowing current of air ispreheated to a considerable degree, in its passage over the hot walls ofthe shell 1 surrounding the combustion space, before it is drawn intothe burners 12. This recuperative or regenerative action of the partsvery considerably diminishes the loss of heat by radiation from theheater jacket, raises the temperature of the gases of combustion, andthus substantially increases both the rapidity and the efliciency of theheating operations. This last result is of particular value andadvantage in the use of the instantaneous type of hot water heater whichis herein illustrated and described.

The upper end of the combustion chamber, containing the burners 12 and21, is partially closed by an annular Lshaped bracket 23 whose uppersurface is provided with two helico-spiral grooved-edge ribs 24 and 26and with an intermediate row of forked supports 25 that are respectivelyadapted to receive and rigidly support the lower turns of threeconcentrically disposed volute coils of pipe which constitute the heatabsorbing elements of the organization. Each of these heating coils ismade up of two tubes 2728, 2930 and 3132, which are wound in parall'elto form a tightly closed volute, or frusto-conical, wall; and thecontiguous or adjacent ends of successive coils are cross connected bythe semi-spiral loops or turns, 33, and 34 (as indicated by dotted linesin Fig. 1) so as to form a continuous twin tube conduit that is coupled,at its upper ,and outer end, to a water inlet fitting 35by means of thesemispiral turn 36 and the manifold 37'and is connected, at its lowerand inner end, to the hot water discharge union 46 by means of thethree-quarter spiral loop 38 and the manifold 39. The outer coil 31-32is surrounded by an annular water jacket 40, whose lower flanged edgerests on the bracket 23 and projects down over the adjacent edge of thelower shell 1; and the upper ends of all three loo coils (27-28, 29-30and 31-32) are covered by a double dome cap 41-42 that is supported andheld in place by the upper flanged edge of this water jacket. The innerdome 42 of the heater cap is provided with a helicospiral grooved edgethat engages closely with the upper turn of the intermediate coil 30;and the inner surface of this dome is preferably lined with a sheet orlayer of insulating or heat resisting material 43, whose lower edgeprojects down inside of the said turn and forms therewith a seal, whichwill prevent the direct passage of the gases of combustion from theupper ends of the coils 27-28 and 29-30 into the space between the twodomes 41-42. The assembled coil, bracket and cap members (27-28, 29-30,

'31-32, 23-24-26 and 41-42-43) constitute, in effect, a return flueboiler which conducts the gases of combustion from the burner chamber inthe shell 1 up through the center of the inner coil 27-28; thencedownwardly through the annular space between the inner coil and theintermediate coil 29-30; and then outwardly and upwardly, around thesupports 25 and through the annular chamber between the intermediate andouter coils, 29-30 and 31-32; and discharges them into the hollow cap 41from which they passto the chimney flue 44.

The lower end of the water jacket 40 is connected to the cold watersupply pipe and the upper end of this jacket is connected to theadjacent extremity of the outer coil 31-32-36-37 by the elbow fittingThe water entering the heater therefore flows upwardly through thejacket 40, then downwardly through the outer coil, then upwardly throughthe intermediate coil and then downwardly again through the inner coil,from which it passes-through the sp ral turns 38 y and the manifoldconnection 39' -to the hot water outlet union 46.

The water discharge fittings-which contain the fuel controlmechanism-are shown in elevation at the right of Fig. 1, and areillustrated in sectional detail in Fig. 3. They comprise a flanged T box47 which is rigidly bolted to the overlapped edges of the shell andjacket members 14-40, and which is joined to the hot water outlet union46 by the short nip 1e 48; and a reducing sleeve coupling 49 w iichconnects the upper outlet of the T with the house service pipe 50. Thelower boss of the fitting 47 is threaded to receive the valve box 19;andthe latter is provided at its lower end with a flanged sleevecoupling 51 which connects the said box with the gas conduit 18. Theflow of gas from the fuel supply pipe 22, through the said box 19 andthe connection 51 to the conduit 18, is

controlled by a downwardly opening valve 52 which is mounted on theupper end of a metal bellows or sylphon member 53 that is attachedto theflanged end of the coupling 51. The interior of the sylphon, 53, is incommunication with the hot water outlet through a lateral passageway 54in the head of the coupling 51, and a pipe union connection 55 betweenthis head and the box 47; and it contains a spring element 56 thatcooperates with the water pressure on the head of the sylphon 53 inholding the valve 52 against its seat. The box 19 also contains a secondsyl phon 57, which is of the same cross sectional area as the sylphon53, and which bears, at its lower end, on the central stem of the valve52. This sylphon 57 is attached to a head 58 which is fitted closely inthe recessed opening on the lower side of the T box 47, and which has acentral hub or boss that projects up into the interior of the said box.This boss is centrally bored to receive a doubleball valve 59-60, .whichis confined therein by the lower beveled end of the vertical Pitot tubeelement 61; and it is also provided with two side passageways 62 and 63,the first of which leads from the opening below the valve 59-60 to theend of a horizontal Pitot tube 64 that is positioned in the center ofthe water discharge passage of thebox 47, and the other of which leadsfrom the opening between the valve heads 59-60 to the interior of thesylphon 57. The double ball valve element is attached to the lower endof a rod 65 that asses up through the opening of the Pitot tu andthrough a central stulfing box in a U- shaped head, 66, which isinterposed and clamped between the parts 47 and 49; and the valve isnormally held in its upper positionshown in Fig. 3-by means of a spring67 that bears on the lower end of the rod 65. The upper extremity ofthis rod is engaged by the top plate of a third sylphon member 68' whichis attached to the upper face of the head 66, and which is enclosed in athin metal cap 69 that is also hermetically secured to the said head;and the space between the sylphon 68 and the cap 69 is partiallyfillede. g., to the level L-with a volatileliquid having a boilin pointwhich isin the neighborhood of the esired temperature of the hot watersupply. The head 66 is laterally perforated with passageways 70-70 etc.,which allow the Water to flow freely from the up er end of the casing 47to theannular'space etween the sleeve 49 and the sylphon cap 69; and itis also provided with a vent or duct 71 which leads from the interior ofthe sylphon 68 to a drain port 72 in the flanged end of the box 47.

The 0 eration of the valve and valve control mec anism last described isas follows: When no liquid is flowingthrough the beaten the pressure ofthe water'inthe two sylphon bellows 53 and 57 is the same and the valve52 is then held in its closed position by the spring thermostat 68-69 isthen insufiicient to overcome the tension of the spring 67 and the valve59-60 closes the opening at the base of the vertical Pitot tube 61 butallows the water to pass freely from the tube 64 through the passages62-63 to the interior of the sylphon 53. If now a house service tap, orother outlet in the line 50, is opened the resulting flow of water pastthe Pitot tube 64 produces a velocity pressure at the open orifice ofthe said tube. which is transmitted to the sylphon 57 and which issuflicient to overbalance both the normal hydrostatic pressure in theconnections 55-5-53 and the tension of the spring 56. The superior forcethus exerted on the head of the upper sylphon opens the valve 52 andpermits the gas to flow into the lower part of the valve box 19 andthence, through the openings 73 in the head 51, to the burner conduit18. When the flow of water is stopped the hydrostatic pressure in thetwo sylphons is again balanced and the "alve 52 is closed by the spring56. If, during the continuation of the flow, the temperature rises abovea certain predetermined point the vapor pressure in the thermostaticchamber 68-69 will become suflicient to overcome the tension of thespring 67 and the valve 59-60 will be forced down thereby shutting offcommunication between the passageways 62 and 63 and openingcommunication between the reversed Pitot tube 61 and the interior of thesylphon 57. The negative velocity or suction pressure at the opening ofthis tube will then be transmitted to the upper bellows and the pressuretherein will be immediately reduced below that in the lower sylphon; andthe valve 62 will be instantaneously closed by the combined effect ofthis difference in pressure and of the spring 56. When the temperatureis again reduced below the point of thermostatic control thecondensation of vapor in the chamber 68-69 permits the spring 67 toagain raise the valve 59-60; the velocity pressure in the Pitot tube 64is again transmitted to the sylphon 57; and the force thus exerted onthe upperside of the valve 52 overcomes the tension of the spring 56 andonce more opens communication between the fuel supply pipe 22 and theburner conduit 18. I

The point at which the thermostatic valve members, 59-60-65, will beshifted-by a change in the temperature of the flowing water-can bevaried within wide limits, either by changing the character of theliquid in the thermostat chamber, or by changing the tension of thespring 67, or both; but in order to provide for varying this point whilethe heater is in continued operation I preferably provide means foralteringthe relative position of the assembled parts 58-67 with respectto the thermostat elements 65- 68-69. In the present exemplification ofmy invention this relative adjustment of the parts is provided for bybeveling the upper surface of the head 58 and interposing between it andthe casing 47 a reversely beveled and transversely movable plate 74 thatcan be shifted laterally by means of the differential screws 75-76.\Vhen adjusted to the desired positions the relatively movable parts areclamped tightly against the casing 47 by means of screws 77-77 etc.which are threaded into ribs on the interior of the box 19; which passdown through the head of the sleeve 51; and are locked in place by nuts78 on the lower side thereof.

Figs. 5 and 6 illustrate modifications of the twin tube conduitconstruction shown in Fig. 1. In the arrangement depicted in Fig. 5 thetwo parallel tubes 3132, which constitute the outer coil (or the tubes27-28 and 29-30 which make up the inner and intermediate coils) arewound in offset or staggered relation to each other-instead of in thevertically superimposed relation shown in Fig. l-and the completed unittakes the form of a double walled helix whose successive turns overlapand interlock in such manner as to both increase the structural rigidityof the coil, and also more effectually retard any transverse leakage ofthe gases of combustion through its interstices. The annular spaces, a.between the contacting sides of the staggered turns may also be filledwith asbestos, or some fibrous cement; and the superimposed edgesthereof may be advantageously brazed or soldered together at intervalsasindicated at w, w-while the coil is being made up. In the modificationshown in Fig. 6 the parallel tubes 27-28 (or 2930 and 31-32) are of ovalor elliptical cross section and are wound in slightly offset andoverlapped relationship; the contiguous sides of these tubes being spotwelded or brazed together (at w, w, etc.) to prevent any accidentaldisplacement of the superimposed turns during the winding, or thesubsequent assembling operations. The use of oval or elliptical pipe, inplace of circular pipe of the same cross-section, increases the ratiobetween the heat absorbing surface of the coil and the volume of theliquid contained therein, and thereby increases the rapidit andeffectiveness of the instantaneous (sicg heating action when the liquidfirst begins to flow through the coils and the gas 1s first turned on.

'The extended absorbing surface which is presented by all of thepreviousl described coil constructions will quickly a stract the largerpart of the heat from the gases of combustion-as they pass up and downbetween the concentric coil walls-and will lower the temperature ofthose gases to below that of boiling water. The steam constltuent of thegases-which results from the combustion of the hydrogen constituents inthe fuel-will therefore be condensed and the water of con- 1,vss,ose

densation will drain back, through suitable orifices in the bracket 23,into the lower part of the heater shell. In order to revent this liquidfrom escaping onto the cor of the room or chamber in which the heater isplaced, the drum 6 is provided with an upwardly extending flange or lip80 to form a pan or basin 81, which may be emptied at suitable intervalsthrou h a drain cock 82. The improved form of urner construction which Iemploy prevents any of this water of condensation from entering themixing tubes 14 even when it collects to the full depth of the an 81;and the retention of this water in the ower part of the heater shell isadvantageous not only on the score of cleanliness, but also because itprevents any injurious overheating of the burner parts and the asconnections thereto. The importance of t is last mentioned feature ofoperation may be realized when it is understood that, inlon continued'periods of o ration, the cap and gauge elements 15-1 may, without suchcoolmg, become almost, or quite, redhot.

The construction shown in Figs. 7 8 and 9 com rises a flanged shell 1",which is open at 'the ottom, and which is provided at the top with arabbeted edge that receives a sheet metal extension 85; and a as supplydrum 6 which fits closely in the lower part of the shell 1, and is suprted on the inturned lower flange thereo by the annular rib 7. A late 3is interposed between the rib 7" an its flanged support,and forms, inconjunction with the contiguous end of the drum 6, an air supplyreservoir at the base of the heater. The shell 1 and the cylindricalextension 85 are surrounded by a concentric sheet metal jacket 4 whichforms therewith an annular air space 5 that is incommunication with thelower air reservoir through a row of portopenings 11" in the shell 1 anda corresponding series of holes 11 in the annular rib 7. The upper endsof the concentric walls 4-85 are covered by a tri 1e walled cap41-8642'* which is provi ed with a series of vertical flues, 87, '87,that afford free communication between the inner chamber of the heatershell and the chimney opening 44", in the top wall 41 of the cap; and asecond row of inclined flues 10, 10 which are located between the upperends of the flues 87-87, and pass through this chimney openin to anenclosed chamber 88 between the intermediate and bottom .walls 8 of thesaid cap. The chamber 88 is in co munication with the upper end of theannular space 5, through the series of peripheral ports 10", 10" etc.;and the con nected passageways and chambers 10--88- 10**-5-11*-11";allow a continuous flow of air from around the hot cap and down the sidewalls of the heater to the air reservoir below the gas supply drum 6.This drum is provided with a cluster of heating burners" connected tothe main fuel supply 12" that are identical in construction with the oneshown in detail in Fig. 4; and it is ipe 22" by means of the conduit 18and t e valve casing 19". When gas is admitted to the drum by the actionof the automatic control mechanism, it passes to the burners 12 and isthere mixed with air that is drawn upward from the lower air reservoir(through the burner stems 13, 13); and the mixed as and air is ignitedby the flame of a suita le pilot light which is constantly supplied withgas through the by-pass connection 20.

The heating coil members which are used in this second illustrativeembodiment of my invention comprise seven flat spirals, 90-91-92-93-94-95 and 96, each one of which is made up of three tubes thatare coiled in vertically superimposed parallel relationship. The sixupper spirals are arranged in three pairs 96-95, 94-93, and 92-91, eachof which is preferabl structed as an integral unit, by ben 'n oroffsetting three parallel tube elements at t eir centers-as indicated at97 etc-and then successively coiling the offset halves of these elementsin opposite directions on a collapsible flanged, or grooved, mandrilwith removable spacing strips interposed between successive turns of thespirals. During the operation of winding-or subsequently, after theremoval of the collapsible mandril frame and the spacing strips from thecompleted unit-the contacting sides of the parallel tube elements may beadvantageousl soldered or brazed or spot welded toget er at intervals-asindicated at win Fig. 10-so as to maintain the said elements in thedesired relationship and also increase the rigidity of the spiral coils.The completed units are suspended in position in the upper part of theheater shell by means of the central rod 98 and the cross bars 99 thatare secured thereto at suitable intervals; and chordally disposed strips100 may, if desired, be interposed between the spirals 96-95, 94-93, and92-91, in order to more firml support the upper portions of these paireor double units.

The ends of the upper and outer turn of the top spiral 96 are slightlyoffset from the plane of the coil and connected to a cold water inletpipe 45 by means of the flared manifold coupling 37; and the inner turnof the bot tom spiral 90 is likewise bent out to one side of the coiland coupled to the hot water disa charge fitting 46" by means of themanifold 39". The outer adjacent ends of the successive spirals, 95 and94,93 and 92, 91 and 90, are

. cross connected in series by suitable manifold and sleeve couplings,101-102-103 etc. that are preferably brazed or welded together; and thecoupled members thus form a continuous conduit through which water flowsfrom the inlet 45 to the center of the upper spiral 96, then outwardlythrough the turns of the spiral 95, then successively inwardly andoutwardly through the coils of the units 9493, and 92-91, and theninwardly again through the turns of the lower spiral 90 to the outletfitting 39 46.

The automatic mechanism for controlling the flow of fuel to the gas drum6 is shown in enlarged sectional detail in Fig. 9. It comprises anupwardly opening valve element 52" which is normally held on its seat inthe casing 19 by the joint action of gravity and of the gas pressure inthe supply pipe 22. This valve is positioned between the adjacent headsof the two sylphon members 53 and 57" which are of the same crosssectional area and which are of substantially the same length. The lowersylphon 53 is mounted on a centrally perforated plate which is clampedin position between the lower end of the casing 19 and a manifoldplug-coupling 51 that is also connected with the cold water pipe 45 (seeFig. 7) and the interior of this sylphon is in constant communicationwith the said pipe through the passage ways vi -55 in the connection 51.The upper sylphon 57 is mounted on a plate 58 which is threaded onto thelower end of a flanged sleeve 58, and which is also clamped in positionbetween the upper end of the box 19 and the elbow fitting 47; and thelatter is coupled to the hot water outlet union 46 by the nipple andunion connection 48 The top of the elbow 47 is connected to the houseservice pipe 50 by an offset cap-coupling 49; and the upper portion ofthis coupling contains a vapor thermostat, that consists of a thin metalshell 69* containing a sylphon element 68*, the space between theseparts being partially filled with a volatile 1i uid L. The lower head66, of the shell 69, is t readed onto the upper end of the sleeve 58";and the upper head of the said shell is provided with a centralextension 7 that passes up throu h the cap 49* and is locked and sealedin ace thereon by the nut and washer 77. T e sleeve 58 is fitted tightlinto a central cross rib in the elbow box 4 and is centrally bored toreceive a hollow balanced plunger valve 59, which is attached to thelower end of a rod that passes up through a stufling box in this sleeve,and bears on the upper plate of the sylphon element 68'. The sleeve isalso provided with an internal annular port 62, that communicates at oneside with the openingin a horizontal Pitot tube 64-which faces inwardly,or

toward the incoming stream of water flowing of fuel to the heaterburners.

104, and is normally held in its upper position (Fig. 9)in which theports 104 are just above the annular port 62, and the lower edge of thevalve is just above the row of ports 63*by the spring 67 The functionalaction of this last described control mechanism is the same as that ofthe one shown in Fig. 3. When the water is at restin the system thehydrostatic pressure in the two sylphons, 53 and 57 is the same; and thevalve 52 is closed. When a house service tap, in the line 50*, is openedand cold water begins to flow through the heater pipes, and outletconnections 4648 47 49 the pressure in the sylphon 57 is reduced by thevelocity suction, or ejector, action of the reversed Pitot tube nozzle61 which is at that time in communication with the interior of the saidsylphon through the ports 63 63 -and the valve 52 is opened by thesuperior pressure in the passage way 54 and the lower sylphon 53 Theopening of this valve permits the fuel to flow from the supply pipe 22,through the conduit 18 and fuel drum 6*, to the burners 12*, where it ismixed with air drawn from the air reservoir below the drum 6, andignited by. the pilot light. The water which flows through the multipletube coils 9690, is quickly raised in temperature by the heat of theburning fuel and when the temperature reaches a predetermined point thevapor pressure in the thermostat cells 6869 overcomes the tension of thespring 67 and the valve 59 is moved downwardly thereby closing the ports63 and simultaneously establishing communication between the ports 62,104 and 63. The pressure in the upper sylphon 57 then becomes equal tothe impact or velocity pressure at the orifice of the Pitot tube 64; andas this pressure exceeds the static pressure in the opening 54' and thelower sylphon 53, the valve 52* is immediately closed and the supplyofgas is cut off from the main heating burners. The resultant drop intemperature in the flowing water reduces the pressure in the thermostat68"69 and the spring 67 lifts the valve 59 to its initial positionthereby cutting off communication between the Pitot tube 64 and thesylphon 57 a and reestablishing connection between that sylphon and thereversed Pitot tube 61. The resulting drop in pressure in the uppersylphon chamber allows the valve 52* to be again opened to admit a freshsupply When the flow of water is stopped the pressure is immediatelyequalized throughout the systemregardless of the final position of thevalve 59" and the main fuel valve 52 is then closed by the joint actionof gravity and of the gas pressure on its upper face.

The predetermined joint of thermostatic cut oil', may be readily variedwithin wide limits by changing the liquid in the vapor pressure cell6869' or by altering the initial tension in the spring 67. This resultmay also be effected by loosening the lock nut 7 7 a ,and revolving thecell 69-thus lowering or tained. Any leakage of liquid through the screwjoint between the head 66 and the sleeve 58or through the sliding jointbetween the stufiing box in the sleeve and the rod 65is drained awaythrough the constantly open ports 71"72 that lead from the space aroundthe thermostat rod 65 to the exterior of the casing 47.

Fig. 10 illustrates a slightly modified form of the triple tube conduitconstruction shown in Fig. 8. In this modification the parallel elementsof the coils 93---94 (or of the other coils 909192-9596) are wound inslightly offset relation-instead of the vertically superimposedrelationship illustrated in Fig. 8-for the purpose of laterallydeflecting and breaking up the rising streams of hot gases, as theypassbetween successive turns of the coils, and thus more continuously andcompletely equalizing the temperature conditions in different parts ofthe heating chamber. The construction shown in Fig. 10 also differs fromthat of Fig. 8 in the vertical spacing relationship between the upperand lower members of the paired coils ;the members 93'94 beingrelatively much closer to each other than the members 9192, 93-94, and

9596; and it will be apparent that the oppositely wound, or right andleft hand, spirals of these coils may, if desired, be allowed to restdirectly on each other and thus avoid all necessity for using anyintermediate supporting or spacing strips, such as are indicated at 100,100 etc.

Figs. 11 and 12 illustrate other forms of automatic control mechanismswhich operate in the same generic manner as those shown in Figs. 3 and9; and which can be used in conjunction with the general organizationsdepicted in Figs. 1 and 2, or Figs. 7 and 8; or in combination withvarious other forms of he iter coil construction-such, for example, asare outlined in Figs. 1 of my earlier Patents Nos. 1,131,021, 1,146,826,1,156,949, 1,- 243,017, 1,248,579, etc.-or, for that matter, in anyanalogous construction of the instantaneous heater type in which thesupply of fuel is controlled and governed jointly by the flow and thetemperature of the water in the heater coils. In the first of thesemechanisms (Fig. 11) the fuel valve 52 is arranged in a verticalposition, and is attached directly to the free end of a horizontalsylphon 53 and is normally held in its closed position against thepressure of the gas in the supply conduit.- 22"by the spring 56". Thesupporting head, 105, of the sylphon 53", is screwed into the bottom ofa recessed pocket, which is formed in the side of the casing 47",

and which is in direct communication with the threaded outlet thatreceives the burner conduit 18'. A valve box 19 is bolted to the outerface of the casing N -in line with the axis of the valve and sylphonelements 52", 53 -and this box contains a second sylphon 57 which isattached to a projecting boss 58 on the side of the box. The centralportion of the casing 47 is bored to receive a double acting poppetvalve, 59"60", which is confined between the head 105 and'an opposinghead 106 which is screwed to the inner face of the casing. The head 105is provided with a central opening 54 which leads from the end of thepoppet valve chamber to the interior of the sylphon 53; and the spacebetween the valve heads 59"60 is in constant communication with theinterior of the sylphon 57 through the angled duct 63"-which leads fromthe body of the casing 17 through the central rib that crosses theopening to the conduit 18 and the cooperating passage way 107 thatpasses down one side of the box 19', through theboss 58", and terminatesin registry with a port in the adjacent head of the said sylphon. Thecentral opening in the head.106which forms a continuation of the cavitycontaining the valve heads 59', 60

is provided with a lateral port that opens into a chamber 108, betweenthe head and the casing 47"; and this chamber is in constantcommunication with the interior of the sylphon 53" through the passageway 109 (dotted) and the port 110. The inner end ofthe valvechamberadjacent the head 60 is provided with a lateral duct 62 whichleads to a vertical Pitot tube 64 that is faced inwardly, or toward thestream of water entering through the nipple connection 48; and the outerend of this same chamber-adjacent the head 59"is provided with a similarduct that communicates with asecond vertically positioned Pitot tube 61that faces upwardly and outwardly, or toward the discharge opening fromthe casing 47. This discharge opening contains a vapor thermostatmember, which consists of a sylphon element 68", an enclosing metal cap69", and a head 66' that is screwed into the upper end of the casing-theclosed chamber between the hermetically sealed parts, 66 68 69", beingpartially filled with a volatile liquid L. The movable head of thesylphon 68? is connected to the stem 65" of the valve 59"60", by meansof the rod 65 and the bell crank lever 74"; and the relative position ofthe connected parts may be adjusted by means of the set screw 76".

When the water is cold, or below the point at which the thermostat isdesigned to act, the

the spring 67 that is interposed between the head of the valve stem 65and the stufiing box, through which the stem passes, in-the head 106.,When there is no discharge of liquid through the casing connections48"47"50 the hydrostatic pressure in the two sylphons, 53 57, isbalanced; and the main fuel valve is then held closed by the spring 56.But whenever an outward flow of water is started (as by opening a tap inthe service pipe 50) the velocity pressure at the opening of the Pitottube 64 is transmitted 'to the outer sylphon 57 through the passage ways6263107--while the pressure in the passage 54 and the inner sylphon 53is simultaneously diminished by the suction or ejector action at theopening of the reversed Pitot tube 61". The opposing pressures on the"alve 52 are thus altered to such an extent as to overcome the tensionof the spring 56", and to completely open the valve, thus admitting thefull supply of fuel to the burner conduit 18". If the temperature of theflowing liquid reaches a predetermined point, the increased vaporpressure in the thermostat member 68"-69 overcomes the tension of thespring 67 and the double action valve 59"60 is moved outwardly. Whenthis movement occurs the valve head 59 will cut off communicationbetween the Pitot tube 61' and the interior of the sylphon 53 andsimultaneously open communication between this tube and the interior ofthe outer sylphon 57 through the passage ways 63107;while the valve head60 will coincidently close the opening between the other Pitot tube 64and the passage 63 and open communication between that tube and thesylphon 53-through the passage ways 62", 108, 109, 110. The velocitypressure conditions in the two sylphon chambers 53 and 57 are thusreverse; and the valve 52 is instantly and firmly closed by the nowpreponderantpressure in the inner sylphon and the cooperating tension ofthe spring 56". If the temperature of the flowing water drops again thecondensation of vapor in the thermostat chamber permits the valve 59"60"to be restored to its initial position by the spring 67"; and apreponderant kinetic or velocity pressure, suflicient to overcome thespring 67 and once more open the valve 52",

is again established in the outer sylphon 57 When the flow of water isstopped, all velocity pressures are immediately eliminated and a uniformhydrostatic pressure is established in the system regardless of theposition of the valve 59 60 thus permitting the valve 52 to be closed bythe action of the spring 56 alone.

In the construction illustrated in Fig. 12 the water discharge openingthrough the casing 47 is made in the form of a Venturi orifice whoseoppositely beveled sides 6461 are respectively in communication with thehot water outlet nozzle 48 and with the lower end of a sleeve coupling49 that connects the said casing with the house service pipe 50.

The coupling 49 contains a vapor thermostat which is similar inconstruction to the ones shown in Figs. 3 and 9 (previously described)and which is supported on an I- shaped base 66 that is clamped inposition between the parts 47 and 49. The lower flange of the base 66 isperforated to' permit the water to flow freely into the lower end of thesleeve 49; and the latter is provided with a helically disposed rib 112which compels the flowing liquid to pass several times around thethermostat shell 69, before it escapes into the service pipe 50. Thebody of the casing 47 is provided with a vertical chamber, which islaterally apertured to receive the main fuel supply pipe 22; and whichis bored and threaded, at its lower end, to carry the valve sleeve 19that is, in turn,

connected with the fuel delivery conduit 18.

The casing chamber and its valve sleeve liner contain two verticallysuperimposed sylphons 53 and 57, the first of which is mounted on a head105 that is bolted against the upper closed end of the chamber, and thesecond of which is supported on a rib 58 that projects from one side ofthe valve sleeve 19. The main fuel valve 52 is interposed between theadjacent ends of the two sylphons 53 and 57 and is preferably integralwith the lower head of the first mentioned element. The casing 47 isfurther provided with a second vertical chamber which is between thesylphon containing recess and the Venturi tube 6461, and which containsa double ball poppet valve 5960, that is confined in place thereinbetween the heads 106 and 114. This poppet valve is attached to a stem65 which passes up through the head 106 and through a stufiing box inthe base 66 and engages with the upper head of the thermostat sylphon68; and it is normally held in its upper positionas shown in Fig. 12bythe adjustable spring elements 657 6 that are mounted in the lower head114. The cavity which contains the upper head 59 of the valve is incommunication with the throat opening of the Venturi tube through a duct115; and the cavity containing the lower head 60 communicates with theupstream end 64 of the tube through a port 116. The interior of theupper sylphon 53 is in communication with the space between the valveheads 5960, through the duct 54 and a port 110 in the head 105; and theinterior of the lower sylphon 57 communicates with the space below thevalve head 60through the passage way 63 the annular channel 117 and thepassage 107and also with the space above the upper head 59, through thepassages 107117-109 (dotted) and 108.

The operation of this last described control mechanism is as follows:When a flow of water is established through the Venturi tube 64-61, thevelocity pressure at the throat of the tube is less than at its upstreamor inlet end 64; and when the poppet valve IS in the position shown inFig. 12in which the pressure in the lower sylphon. This condiliverypipes 22 and 18. The sy tion will remain unchanged until the temperatureof the flowing water is raised to such a point that the resultant vaporpressure in the thermostat chamber 6869 overcomes the preadjustedtension of the spring 65, and moves the poppet valve downward to itslower position. This movement shuts off communication between the port116 and the interior of the lower sylphon 57, and simultaneouslyestablishes a connection between this port and the passage ways 54 and110 which lead to the sylphon 53; and'the same movement coincidentlyshuts off communication between the throat duct 115 and the uppersylphon, and opens communication be tween this duct and the ports andpassages,

108109117 and 107, which lead to the lower sylphon. Under suchcircumstances the upper side of the main valve 52 is subjected to thepreponderant velocity pressure at the inflow or upstream side of theVenturi tube 6461; and this pressure cooperates with the action ofgravity, and of the gas pressure in the supply pipe.22, in quickly andpositively closing the said main valve. When the temperature of theflowing water falls below the point of thermostatic cut off. thecondensation of vapor in the chamber 6869 permits the spring 65 torestore the poppet valve 5960 to its upper position, and to thusreestablish the first described pressure conditions ;in consequence ofwhich the valve 52 is again opened. When the flow of water through thecasing 47 is stopped the hydrostatic pressures are at once equalized inall of the passages and chambers of the casing 47; and the main valve 52will then be closed by the action of gravity (supplemented by the gaspressure on its upper side) regardless of the position of the poppetvalve 5960.

Fig. 13 illustrates another simple and eflicientconstruction, in whichthe variation of the velocity pressure at different points in a Venturidischarge tube is utilized to control the opening and closing-of a mainsupply val In this exemplification of my present improvements the lastnamed valve (here indicated at 52) is located in a valve chamber 19,which is separate and distinct from the one containing the actuatingsylphon 57, and which is provided with end and side apertures to receivethe fuel sup ly and del phon 57 is mounted on a head 58 that is screwedinto the side of the main casing 47; and the latter is connected to thewater outlet from the heater, or other device with which it is used, bythe nipple 48. The Venturi tube opening 6461 leads from this connectionto a lateral aperture in the upper wall of the casing 47, which isthreaded to receive the sleeve coupling 49 that carries the lower end ofthe service discharge pipe 50. The sleeve 49 is provided on its innersurface with a helical rib or vane 112 that closely embraces the outershell of a vapor thermostat element 6869; and the latter is providedwith a head 66 which is mounted on a short annular support 120, thatprojects up from the floor of the water passage on the down stream sideof the Venturi tube. The body of the casing is also provided with acentral chamber which contains a short poppet valve element 59, that isconfined therein by the elongated head 106; and this valve isoperatively connected to the thermostat element 68 by means of the valvestem 65. the bell crank lever 74 and the vertical rod 65. The valve isnormally held in its left hand position (shown in Fig. 13)

by the spring 65; spring, as well as the operative relation of theconnecting elements, 657465, can be adjusted by the nuts 76.

The actuating sylphon member 57 is in this case mounted in a closedchamber and is exposed to water pressure on both its interior andexterior. The interior of the sylphon is in constant communication withthe opening 116, at the upstream or inlet side of the Venturi tube,6461, through the duct 63, the \annular channel 117 and the passage 107;

and the chamber surrounding the sylphon is normally connected to thethroat opening 115, of the Venturi tube, through the port 54 and thecavity containing the poppet valve 59. The free end of this sylphon isoperatively connected to the main fuel valve 52 by means of the rod 121which passes through a stuffing box in the closed end of the sylphonchamber, and through an unpacked aperture in the adjacent wall of thevalve box 19, and is provided with an adjustable washer 122; and thesaid valve is normally held closed by a spring 56 that is interposedbetween it and a removable cross bar 123. But when a stream of waterflows through the Venturi tube 6461 (with the valve 59 in its indicatedposition) the hydrostatically 'equal water pressure on the two sides ofthe sylphon 57 are unbalanced; and the preponderant velocity pressure atthe upstream port 116 ted to flow from the pipe 22 into the front end ofthe box 19 and thence to the conduit and the tension of this,

18. This movement brings the washer 122 into pressure engagement withthe'adjacent outer face of the valve box 19 and prevents any leakage ofgas from the opening through which the rod 121 passes. When thetemperature of the flowing water exceeds a pre-' both sides,-viz, thevelocity pressure at the upstream orifice 116 and the main valve 52 willbe closed by the joint action of the spring 56 and the gas pressure inthe pipe 22. A subsequent drop in temperature results in a restorationof the poppet valve to its initial position, and a reestablishment of anexcess or preponderant velocity pressure on the interior of the sylphon57' which will overcome the initial tension of the valve spring 56 andagain open the main valve 52. When the flow of water stopsthehydrostatic pressures are at once equalized in all of the passage waysand chambers of the casing 47 and the main valve 52 will then be closed,regardless of the position of the temperature controlled poppet valve59.

All of the illustrative control mechanisms which have been described-i.e., those shown separately in Figs. 3, 9, 11, 12 and l3are characterizedby the same generic mode of operation, although they differ quite widelyfrom one another in structural form. In all cases the actuating forcesthat control, or effeet, the opening and closing of the main fuelcontrol valve of the system, are what are termed velocity pressures,which are produced or set up by the flow of a stream of liquid over orpast restricted orifices that lead to volumetrically variable chamberslocated outside of the main stream flow. These velocity pressures areprimarily functions of the speed of movement of the flowing water withrespect to the axes of the orifices at which they are established; andthey are not dependent upon the actual passage of liquid into or throughthe said orifices; although some slight movement of this naturenecessarily accompanies any change in volume in the chambers to whichthey lead. The functional mode of action of my improved velocitycontrolled mechanism is thus difl'erentiated and distinguished frompreviously used devices in which a control member is actuated by thepressure of a water stream against a piston or check valve elementas inthe well known Ruud-Pittsburgh type of instan aneous water heaterconstructionor in which such a member is actuated by hydraulicdifferences in head at separated points in the water stream-asexemplified in the Braith- Waite-Wadsworth type of control apparatus.One of the marked advantages of the present invention is thatsubstantially different velocity pressures may be produced at pointswhere the difference in hydraulic head are negligible-by the hereindescribed use of Pitot or Venturi tubes or equivalent deviceswithoutinterposing any physical obstruction, or any substantial functionalresistance, to the free flow of water through the system. I am thusenabled to produce a very compact, self contained, and powerful controlmechanism which will act very quickly in both opening and closing thesupply valve member, without in any way throttling the continuouspassage of liquid through the heater coils; and one which will not besensibly affected in its action by any changes in either the hydrostaticor hydraulic pressures in the water supply or the water dischargeconduits.

It will further be observed that all of the heater coil constructionswhich I have herein illustrated and described are characterized by theuse of multiple tube conduits; viz, by the use of liquid conductors.which are made up of two or more pipes that are wound and connected inparallel. Some of the advantages of this feature of my improvements arediagrammatically indicated in Figs. 14 and 15. The wall thickness, T, ofa circular pipe which is capable of withstanding a given internalpressure is proportional to the mean diameter, D, of the pipe. Theweight of such a pipe-when the wall is thinis proportional to thethickness and the diameter; and, for a given bursting strength, thisweight is therefore proportional to the square of the diameter. But. thecross sectional area of the pipe is also proportional to the square ofthe diameter; and for a given carrying capacity (i. e., a given volumeof discharge at a given pressure) the weight of the conduit per unitlength is therefore constant regardless of whether it may be made fromone tube or from a number of tubes joined in parallel. But the heatabsorbing and conducting surfaces of N tubes joined in parallel isgreater than that of one larger tube of the same cross sectional area inthe proportion of 1: /N. A twin conduit such as is shown in Figs. 1, 5or 14, has therefore more than 40% greater surface area than a singletube of the same carrying capacity and length; and a triple tubeconductor-like that shown in Figs. 8, 10 or 15has nearly 75% greaterexposed area than such a single tube. The rate of conduction of heatfrom a gaseous medium to a liquid is proportional not only to thesurface area of contact, but also to the thickness of the wall betweenthe two media;

and since the wall. thickness of the multiple one tube conduit in theproportion of 1 z /N, the heat absorbing capacity of the twin tube andtriple tube constructions may be, respectively, more than 60%, and morethan 100%, 5 greater than that of the usual form of single- 7 tubeheating coils of the same length, weight,

and cross-sectional area.

In the case of elliptical or flattened tubes (like those shown in Fig.6) the ratio between 10 the surface area of the single circular pipeconduit and the multiple oval-tube conduit of the same aggregate crosssection and length is even greater than 1: /Ne. g., it may be as largeas 1 N but the thickness and weight of an oval or elliptical conductormust be greater than that of a circular conductor of the same carryingcapacity and length (unless the material is different), and this factsomewhat increases the thermal resistance of the oval tube walls to heattransmission. The heat absorbing capacity of a twin oval-tubeconstruction is therefore intermediate that of the twin-tube and.triple-tube coils shown in Figs. 1-14 and 815 (or alternatively in Figs.5 and 10).

The great increase in heat absorbing power of all the multiple tubeconstructions considered above cooperates With the increased temperatureof the gases of combustion resulting from the use of a preheating airjacket and of the improved burner construction heretofore describedinaccelerating the so-called instantaneous action of the organization, andin increasing its thermal efficiency; But regarded from another viewpoint the augmented heat absorption of my improved multiple tubeconstruction makes it possible to very substantially reduce the lengthand the corresponding weight of the heating coils without reducing thepresent standard of thermal efficiency; and when copper is used as amaterial for these coils (as is the usual practice) the saving in thefirst cost of this item alone is a very material and important one. Itis further possibleby the use of multiple tube coil unitsto substitutecold drawn steel tubing for the now commonly used copper tubing; andthereby efl'ect r0 further. economies in manufacture and operationsincethe bursting strength of such steel tubing is in excess of that requiredin normal practice and the advantages of using tubes of flattened, orelliptical cross section like those shown in Fig. 6) can be obtainedwithout the disadvantage of any increased weight per unit length. a

It will also be apparent 'tothose skilled in this art that the greatlyincreased heating etliciency of my improved constructionswhich resultsfrom the combination of means for preheating the air supplied to theburners with the means for. more rapidly and completely utilizing thegreater heat thus generated in raising the temperature of the liquid inthe heater coilsalso augments the effectiveness of the thermostaticcontrol means for governing the supply of fuel to the apparatus inaccordance with the variations in the temperature of the flowing liquidand thereby maintaining that temperature at the desired point. The airpreheating means, the heat absorbing means, and the temperature controlmeans all coact and mutually cooperate to effect the desired result;viz, the raising of the water in the heater to the desired temperaturein the shortest possible time and the reduction in the time fluctuationsin that temperature to, the greatest attainable degree. r

Othercharacteristic and novel features, and other specific advantages,of the various illustrative organizations herein described, will now beapparent to those skilled in the art to which the present inventionappertains; and

with the preceding disclosure as a guide the parts and elements of myimproved combinations may be readily modified and rearranged, to bestmeet special conditions of service, by any mechanic or engineer who isfamiliar with the construction and operation of the types of. apparatusin which these improvements-or any part of them-may be advantageouslyutilized. The accompanying drawings and descriptions are therefore to beconsidered as only illustrative of the many organizations which mayembody my present invention; and they are not to be regarded as imposingper se any limitations on the scope of application thereof. t

\Vhat I claim, in this connection, is:

1. In a water heater the combination of a heating coil comprising aplurality of hollow conductors disposed in substantial contact with eachother throughout their length and connected in parallel at their ends toform a multiple tube conduit, a fuel burner positioned below said coil,means for enclosing the a said coil and the said burner and forpreventing any direct access of theexternal air thereto,and meansjointly controlled by the flow and by the temperature of the liquid asit emerges from the multiple tube conduit, for varying the supply offuel to the said burner and the resultant application of heat to thesaid conduit.

2. In a water heater the combination of a heating coil, open connectionsof substantially unchanged area between the ends of said coil and theinlet and outlet passages therefor and affording an unimpeded passagefor the flow of fluid therethrough, a heating burner for the said coil,a valve for controlling the supply of fuel to the said burner, and meansresponsive to differences in velocity pressure *at-*ad acent points inthe stream of liquid flowing through the said coil connections andacting to open or close the said valve when the temperature of'saidliquid is respectively below or above a predetermined point.

3. In a water heater the combination of a heating coil, a fuel burnerpositioned below the said coil, a, valve placed in the fuel supply lineto the said burner, a pair of volumetrlcally .variable vesselspositioned on opposite sides of the said valve, and means responsive tochanges in velocity at adjacent points in the stream of liquid flowingthrough said coil and acting to vary the pressure in one of the saidvessels and thereby open the said valve when the temperature of theflowing liquid is below a predetermined point.

4. In a water heater the combination of a heating coil, a fuelburneradjacent thereto, a valve controlling the supply of fuel to thesaid burner, a pair of sylphon bellows positioned on opposite sides ofthe said valve, passage ways leading from the said bellows to twoadjacent points in the outlet passage from the said coil, a thermostatpositioned in the said outlet passage, and means controlled by saidthermostat for opening and closing one-of said passage ways in responseto variations in temperature.

5. In a water heater thecombination of a multiple tube heatingcoil,continuously open connections between both ends of the said coil and awater supply circuit and providing for an unimpeded flow of liquidtherethrough, a plurality of heating burners therefor, a valvecontrolling the flow of fuel to the said burners, means for normallyholding said valve closed when the liquid in the heater coils is at restor is above a predetermined temperature, and means responsive to avelocity pressure produced by the flow of liquid over two adjacentorifices and acting to open said valve when the flowing liquid is belowsaid predetermined temperature. I

6. In a water heater the combination of a heating'coil, a burnertherefor, a valve controlling the supply of fuel to the said burner,means for creating differences in velocity pressure at closely adjacentpoints in the outlet passage from said coil, pressure ducts leading fromsaid points to pres ure chambers on opposite sides of said fuel :valve,a thermo stat in said outlet passage, and means actu ated by saidthermostat for controlling the flow of liquid through one or more of thesaid ducts for the purpose specified.

7. In a water heater the combination of a heating coil,.a fuel burneradjacent thereto, a valve for varying the supply of fuel tothe saidburner, and a temperature controlledmechariis'm for'governing themovements of the said valve and comprising means for creatingdifferences in velocity pressure at adjacent points in the waterpassage, an auxiliary valve chamber, ducts leading therefrom to the saidpoints, a volumet'rically variable vessel in communication with the saidchamber, a thermostat positioned in said water passage, and an auxiliaryvalve actuated by said thermostat for controlling communication betweenthe said ducts and the said vessel.

8. In a water heater the combination of a heating coil, a heating burnertherefor, and means for varying the supply of fuel to the said burnerwhich comprises a Venturi tube in the water passage, a water chamber,ducts leading therefrom to the throat and up stream orifices of the saidtube, a volumetrically variable vessel connected with said chamber, ,avalve therein, and means actuated by the change in temperature in thewater passage for moving said valve and thereby controllingcommunication between said vessel and the said ducts.

9. In a water heater the combination of a hollow shell closed at itslower end, a heating coil mounted therein, a fuel burner positionedbetween the said coil and the closed lower end of the said shell andforming therewith an air reservoir, an air jacket surrounding the saidshell and in communication with the said reservoir, and a multiplewalled cap conjoining the upper ends of the said shell and the saidjacket wall.

In testimony whereof I have hereunto set my hand.

FRANK L. O. WADSWORTH.

